Fix GCC 4.7 errors

GCC 4.7.2 fail overriding constructors defined with virtual and default.
Debian build also fails linking  without -lrt.
INT64_C is not defined on Debian with 4.7.2. "ll" should be enough.

Change-Id: Ia779f094ed64fc3b1941429485e81520d017c2f5
Reviewed-on: https://weave-review.googlesource.com/1671
Reviewed-by: Alex Vakulenko <avakulenko@google.com>
diff --git a/src/notification/xmpp_stream_parser.h b/src/notification/xmpp_stream_parser.h
index 41faaff..b8f5723 100644
--- a/src/notification/xmpp_stream_parser.h
+++ b/src/notification/xmpp_stream_parser.h
@@ -49,7 +49,7 @@
     virtual void OnStanza(std::unique_ptr<XmlNode> stanza) = 0;
 
    protected:
-    virtual ~Delegate() = default;
+    virtual ~Delegate() {}
   };
 
   explicit XmppStreamParser(Delegate* delegate);